1. Field of the Invention
The present invention generally relates to a substrate processing apparatus and method for performing predetermined processing on a substrate by utilizing a chemical reaction in the inside of a reaction enclosure. Incidentally, for example, an enclosure of double structure is used as the reaction enclosure. Further, for instance, CVD (Chemical Vapor Deposition) processing is adopted as the predetermined processing. Furthermore, for example, a thermal CVD processing or a plasma CVD processing is employed as this CVD processing.
2. Description of the Related Art
Generally, a film deposition apparatus for forming a predetermined thin film on a surface of a wafer is needed for producing a semiconductor device.
Example of this film deposition apparatus is CVD apparatus for performing film deposition by utilizing a chemical reaction in a hermetically enclosed reaction space.
Further, an example of such a CVD apparatus is a batch type CVD apparatus for forming predetermined thin films on a plurality of wafers at a time.
Furthermore, an example of such a batch type CVD apparatus is a vertical CVD apparatus wherein the plurality of wafers, on each of which thin film should be formed, are placed by being arranged vertically so that the horizontal sections of the wafers overlap with one another.
In the case of this vertical CVD apparatus, for instance, a reaction furnace of double structure, which has an outer tube and an inner tube, is used as the reaction enclosure.
In the vertical CVD apparatus using a reaction furnace of double structure as the reaction enclosure, a carrying-in/carrying-out opening is usually provided in the bottom end portion of the reaction furnace. Further, in this CVD apparatus, reaction gas for film deposition is usually supplied from the bottom end portion of the reaction furnace. Moreover, atmosphere contained in the inside of the reaction furnace is evacuated from the top end portion thereof through a space provided between the outer tube and the inner tube.
FIG. 13 is a side sectional diagram showing the configuration of the conventional vertical CVD apparatus which has the aforementioned reaction furnace of double structure. Hereinafter, the configuration of this conventional vertical CVD apparatus will be described. Incidentally, in the following description, this vertical CVD apparatus will be described as a low pressure CVD apparatus.
Vertical CVD apparatus 100 shown in this figure has: a reaction system 110 for forming a predetermined thin film on a wafer W by utilizing a chemical reaction in the inside (reaction space) of a reaction chamber 1a; a carrier system 120 for carrying the wafer W into the reaction chamber 1a and for carrying the wafer W therefrom; a gas supply system 130 of supplying into the reaction chamber a reaction gas for a film deposition process, an inert gas for performing what is called an after-purging process, and an inert gas for performing what is called an atmosphere restoring process; and an exhaust system 140 for the vacuum exhaust process (namely, the vacuum pumping process) of the reaction chamber 1a.
Incidentally, the after-purging process is defined herein as a process consisting of the steps of supplying an inert gas into the reaction chamber 1a, and performing the vacuum-pumping of the reaction chamber 1a upon completion of the film deposition process, thereby purging the atmosphere away from the reaction chamber 1a by using the inert gas. Moreover, atmosphere restoring process is defined herein as a process consisting of the steps of stopping the vacuum exhaust process upon completion of the after-purging process, and then supplying an inert gas to the reaction chamber 1a, thereby restoring the inner pressure of the reaction chamber 1a to atmospheric pressure. This atmosphere restoring process is a process for preparing the apparatus for discharging the wafer W from the inside of the reaction chamber 1a.
The reaction system 110 has a reaction furnace 111 for forming the reaction chamber 1a. This reaction furnace 111 is configured as a reaction furnace of double structure that has an outer tube 1M and an inner tube 2M. Throat 2a, through which a wafer W is carried in or out, is provided in the bottom end portion of this reaction furnace 111.
Gas supply system 130 has a gas supply nozzle 131 that is used to supply a reaction gas for the film deposition process, an inert gas for the after-purging process, and another inert gas for the ambient gas restoring process. Gas blowoff opening 4a of this gas supply nozzle 131 is provided in the neighborhood of the throat 2a of the furnace 111.
Exhaust system 140 has a main exhaust line 141 for performing a primary exhaust operation, an over-pressurization preventing line 142 for performing an over-pressurization preventing operation, and a bypass line 143 for performing a slow exhaust operation.
Incidentally, the primary exhaust operation is herein defined as an operation of performing a vacuum exhaust process on the reaction chamber 1a at high speed by increasing the exhaust conductance thereof. Further, the over-pressurization preventing operation is a vacuum exhaust process preventing the inner pressure of the reaction chamber 1a from exceeding atmospheric pressure in the atmosphere restoring process upon completion of the after-purging process. Moreover, the slow exhaust operation is herein defined as an operation of performing the vacuum exhaust process of the reaction chamber 1a at low speed by decreasing the exhaust conductance thereof.
Atmosphere exhaust port 5a of the exhaust system 140 is provided at a place where an atmosphere contained in the inside of the reaction chamber 1a is exhausted from the bottom end portion thereof through the space 3a between the outer tube 1M and the inner tube 2M.
In the case of the apparatus of the aforementioned configuration, when performing the film deposition process, first, a wafer W to be used therefor is carried into the reaction chamber 1a by the carrier system 120. Upon completion of this carrying--into operation, a slow exhaust operation is performed on the reaction chamber 1a by a bypass line 143. In this case, the atmosphere in the reaction chamber 1a is discharged from top end portion of the reaction furnace 111 through a space 3a between the outer tube 1M and the inner tube 2M.
When the degree of vacuum reaches a predetermined value as a result of a vacuum pumping process, a reaction gas for the film deposition is supplied by the gas supply system 130 to the vicinity of the throat 2a. Further, a primary exhaust operation is performed on the reaction chamber 1a by using a primary exhaust line 141. Thus, the reaction gas flows from the bottom portion (namely, a gas supply side) of the reaction furnace 111 to the top portion (namely, an exhaust side) and is dispersed into the reaction chamber 1a. As a consequence, predetermined thin film is formed on the surface of the wafer W. Moreover, an unreacted gas (namely, a part of the reaction gas, which does not react chemically) and the vapor of a reaction by-product are discharged from the top portion of the reaction furnace 111 through the space 3a.
When predetermined thin film is deposited on the surface of the wafer W, an inert gas is supplied by the gas supply system 130 to the reaction chamber 1a. At that time, the primary exhaust operation having been performed by the line 141 is continued without interruption. Consequently, the atmosphere in the reaction chamber 1a is purged by the inert gas. Upon completion of this after-purging process, the primary exhaust operation is terminated. Thus, only the operation of supplying the inert gas is continued. Thereby, the internal pressure of the reaction chamber 1a is increased.
When the internal pressure of the reaction chamber 1a exceeds atmospheric pressure, a vacuum exhaust process is performed on the reaction chamber 1a by the over-pressurization preventing line 142. Thus, the internal pressure of the reaction chamber 1a is maintained at atmospheric pressure. Thereafter, the operations of supplying the inert gas and preventing the over-pressurization are terminated with predetermined timing. Then, the wafer W, on which thin film is deposited, is carried out of the reaction chamber 1a.
In the herein-above description, there has described the configuration and operation of the conventional vertical CVD apparatus that has the reaction furnace 111 of the double structure.
However, in the case of the conventional vertical CVD apparatus 100 of the aforementioned configuration, during a time period when the inside of the reaction chamber 1a is opened to the outside through the throat 2a, outside air enters the inside of the reaction chamber 1a through this entrance 2a. Moreover, a gas-phase backward flow enters the reaction chamber 1a from an atmosphere exhaust path of the exhaust system 140. Thus, the vertical CVD apparatus has encountered the following four problems that
(1) First, during the time the inside of the reaction chamber 1a is opened to the outside through the throat 2a, the outside air enters the inside of the reaction chamber 1a. Thus, the inside of the reaction chamber 1a is contaminated.
(2) Second, during the time the inside of the reaction chamber 1a is opened to the outside through the throat 2a, the outside air enters the inside of the reaction chamber 1a. Thus, particles are generated in the reaction chamber 1a.
Namely, even after the after-purging process is performed, a trace amount of unreacted gas is present in the reaction chamber 1a as a residue. When the outside air enters the inside of the reaction chamber 1a, this unreacted gas is mixed with water vapor contained in this outside air. This results in the generation of a contaminant. This contaminant acts as the particle. Therefore, when the outside air enters the inside of the reaction chamber 1a during the time the inside of the reaction chamber 1a is opened to the outside through the throat 2a, the particles are generated in the reaction chamber 1a.
(3) Third, when performing the film deposition process, a haze (or mist) is generated on the surface of a wafer W in the case that the outside air enters the inside of the reaction chamber 1a during the time the inside of the reaction chamber 1a is opened to the outside through the entrance 2a.
Namely, when the outside air enters the inside of the reaction chamber 1a during the time the inside of the reaction chamber 1a is opened to the outside through the throat 2a, vapor (outgassed), which is generated from a reaction by-product stuck onto the inner wall in the vicinity of the throat 2a, flows backward into the reaction chamber 1a. Thus, when forming film, a haze is produced due to this vapor on the surface of a wafer W.
(4) Fourth, in a time period during which the inside of the reaction chamber 1a is opened to the outside through the throat 2a, the inside of the reaction chamber 1a is contaminated by the gas-phase backward flow from the atmosphere exhaust path of the exhaust system 140 thereto.
Namely, when coming into contact with a low-temperature portion during discharge through the atmosphere exhaust path of the exhaust system 140, the unreacted gas or the vapor generated from the reaction by-product solidifies. This solidified gas is stuck onto the internal metallic surface of the atmosphere exhaust path or onto the quartz members therein as a reaction by-product. When the amount of this deposited by-product becomes large, this by-product may peel off the inner surface of the exhaust path and become particles.
Thus, in a time period during which the inside of the reaction chamber 1a is opened to the outside through the throat 2a, such particles flow from the atmosphere exhaust path of the exhaust system 140 into the inside of the reaction chamber 1a when the gas-phase backward flow enters the inside of the reaction chamber 1a from the atmosphere exhaust path of the exhaust system 140. As a result, the inside of the reaction chamber 1a is contaminated.
The present invention is accomplished to solve the aforementioned problems of the conventional apparatus and method.